Propellant compositions comprising nitramine oxidants

ABSTRACT

The present invention relates to a high energy-containing propellant composition and a use thereof. The propellant composition of the present invention is a propellant composition for guns, including: (a) 55 to 85 wt % of a nitrocellulose binder; (b) 10 to 35 wt % of a nitramine oxidant; (c) 1 to 4 wt % of a plasticizer having both a nitrate group and a nitramine group; and (d) 0.5 to 3 wt % of a stabilizer. The propellant composition of the present invention significantly improves a physical compatibility between the nitrocellulose binder and the oxidant using a plasticizer containing both a nitrate group and a nitramine group, leading to stable interior ballistics characteristics from low temperature to high temperature as well as improvement on the characteristics of an extrudate. Accordingly, the propellant composition of the present invention may be effectively applied to an ammunition for guns due to an excellent physical property and interior ballistic stability thereof.

CROSS-REFERENCE TO RELATED APPLICATION

Pursuant to 35 U.S.C. §119(a), this application claims the benefit of earlier filing date and right of priority to Korean Application No. 10-2016-0018434, filed on Feb. 17, 2016, the contents of which are incorporated by reference herein in its entirety.

FIELD OF THE INVENTION

The present invention relates to a high energy-containing propellant composition and a use thereof.

BACKGROUND OF THE INVENTION

Propellants for use in guns are composed of various components, and for propellant compositions developed in the past, there were numerous compositions using materials which are toxic or suspected of causing cancer. There is a tendency that hazardous materials are not used in propellant compositions being recently developed. Among additives frequently used so far, diphenylamine (DPA) is toxic enough to cause inhibition of erythrocytopoiesis, spleen injury, and so on, and suspected as a carcinogen, which is a stabilizer of an oxidant having a nitrate group. Dinitrotoluene (DNT) has an extremely high toxicity to destroy erythrocytes, and butyl phthalate (DBP) is used as a plasticizer, irritates the eyes, the skin, and the like, and causes nausea when inhaled.

Single base propellants including nitrocellulose (chemical name: cellulose nitrate) as a main component have been developed, and in order to increase the rate of converting the energy of the propellant into the kinetic energy of the projectile, the energy-release rate of the propellant is controlled through design optimization of the propellant shape and coating on the propellant surface, and so forth. However, since the single base propellants do not satisfy the requirements of the weapon system which requires an increase in muzzle energy, a double base propellant composition has been developed, which is produced by adding to nitrocellulose an energetic plasticizer such as nitroglycerin having an energy group in the molecular structure.

In the double base propellant composition, the energy of the propellant is much higher than that of the single base propellant, but there is a problem that the double base propellant composition is vulnerable to bullet impact, fire outbreak, and the like. Further, in that a phenomenon in which an energetic plasticizer such as nitroglycerin is precipitated on nitrocellulose occurs due to the migration of energetic plasticizer when time elapses, there has been a problem in that interior ballistics characteristics are changed. Various attempts to solve the problem have been made, and the most appropriate method is to add a nitramine-based oxidant having high energy to a composition including nitrocellulose as a main component. The composition has not only energy which is as high as the level of the double base propellant but also no migration problem of nitroglycerin, and shows that the stability thereof against bullet impact and fire outbreak is much more excellent than that of the double base propellant. However, in a case that a nitramine solid oxidant is added to a nitrocellulose, the physical compatibility of the nitrocellulose having a nitrate group with the solid oxidant having a nitramine group is so insufficient that a phenomenon in which bubbles are generated or the surface of an extrudate splits occurs when the propellant shape is designed and extruded. In addition, the mechanical strength of the prepared propellant is so insufficient that when the propellant is environmentally treated at normal temperature, high temperature or low temperature and discharged, a sharp increase in pressure is likely to occur. In particular, the propellant is damaged at low temperature when the strength thereof is insufficient, and the pressure in the gun barrel is sharply increased because of the increase of burning surface of the propellant due to the damage, thereby making it difficult to use the propellant in a low-temperature environment. In order to prevent the disadvantage, attempts to introduce a nitramine solid oxidant have been made by massively adding to a nitrocellulose a plasticizer which does not contain energy, such as di-n-bytyl phthalate (DBP), di-2-ethylhexyl adipate (DOA), di-2-ethylhexyl phthalate (DOP) for softening of the nitrocellulose. When performing the treatment, conventional problems do not occur during the preparation of the propellant, but a phenomenon is developed, in which the plasticizer moves to the surface of the propellant and ends up with precipitation on the surface as time elapses. When the plasticizer is precipitated on the surface of the propellant in this manner, there occurs a problem that interior ballistics characteristics of the propellant are changed.

There are urgent needs in the art for a more efficient propellant composition which may solve the above-described various problems.

SUMMARY OF THE INVENTION

The present inventors have endeavored to develop a propellant composition which may be effectively used for guns. As a result, the present inventors have confirmed that a propellant composition was prepared by adding a plasticizer having both a nitrate group and a nitramine group in small amounts, and the composition not only improves the physical compatibility between nitrocellulose and a nitramine oxidant to exhibit excellent extrusion characteristics which do not show a phenomenon such as bubble generation and clogging of perforation holes, but also when the composition is applied to ammunition, stable interior ballistics characteristics may be imparted to the ammunition from low temperature to high temperature to effectively use the composition for a high-performance ammunition, thereby completing the present invention.

Therefore, an object of the present invention is to provide a propellant composition for guns.

Other objects and advantages of the present invention will be more apparent from the following detailed description together with the appended claims and drawings.

In one aspect of this invention, there is provided a propellant composition for guns, including: (a) 55 to 85 wt % of a nitrocellulose binder; (b) 10 to 35 wt % of a nitramine oxidant; (c) 1 to 4 wt % of a plasticizer having both a nitrate group and a nitramine group; and (d) 0.5 to 3 wt % of a stabilizer.

The present inventors have endeavored to develop a propellant composition which may be effectively used for guns. As a result, the present inventors have confirmed that a propellant composition was prepared by adding a plasticizer having both a nitrate group and a nitramine group in small amounts, and the composition not only improves the physical compatibility between nitrocellulose and a nitramine oxidant to exhibit excellent extrusion characteristics which do not show a phenomenon such as bubble generation and clogging of perforation holes, but also when the composition is applied to ammunition, stable interior ballistics characteristics may be imparted to the ammunition from low temperature to high temperature to effectively use the composition for a high-performance ammunition.

Typically, a propellant composition for use in guns includes: (i) a binder; (ii) an oxidant or a raw material powder; and (iii) an additive. Since components constituting a conventional propellant composition include hazardous materials in a body, there is an urgent need for improvement in this matter. In this regard, the present inventors have devised/prepared a propellant composition for guns, in which high energy and insensitive properties are improved using a raw material which is non-toxic to the human body for the health of ammunition manufacturers and solders handling weapons. Specifically, the propellant composition of this invention includes: (a) a nitrocellulose binder; (b) a nitramine oxidant; (c) a plasticizer having both a nitrate group and a nitramine group; and (d) a stabilizer.

The nitrocellulose binder of the present invention is a material which forms a matrix structure in the propellant composition, and is bonded to an additive such as an oxidant and a stabilizer to give a physical stability to the propellant in a shrinking and swelling environment depending on the change in temperature. As the nitrocellulose binder used in the present invention, a nitrocellulose having a nitrogen content of 12 to 14 weight % (wt %) is preferred. For example, a nitrocellulose including a nitrogen content of 13.1 wt % may be used alone, or also be prepared and used by appropriately mixing a nitrocellulose including a nitrogen content of 12.6 wt % and a nitrocellulose including a nitrogen content of 11.3 wt %.

In a certain embodiment, the nitrocellulose binder contained in the propellant composition of the present invention may be included in an amount of 40 to 95 wt %, more specifically 50 to 90 wt %, and even more specifically 55 to 85 wt % in the total weight, but the content is not limited thereto.

According to the present invention, the oxidant used in the propellant composition of the present invention maximizes the performance of the propellant for guns using a nitramine oxidant. The nitramine oxidant has an average particle size of 6 μm or less. It is not preferred in the senses that when the size is larger than the aforementioned size, insensitive properties is deteriorated, and when pressure is increased, there is a drawback in that the burning rate is sharply increased to induce high chamber pressure. Specifically, the nitramine oxidant is not particularly limited as long as the oxidant has an average particle size of 6 μm or less publicly known in the art, and includes cyclotrimethylenetrinitramine (RDX), cyclotetramethylene tetranitramine (HMX), hexanitrohexaazaisowurtzitane (CL-20) and ethylene dinitramine (EDNA), but are not limited thereto.

In a certain embodiment, the nitramine oxidant added to the propellant composition of the present invention is at least one oxidant selected from cyclotrimethylenetrinitramine, cyclotetramethylene tetranitramine and hexanitrohexaazaisowurtzitane, or a mixture of two or more thereof, and more specifically, includes one oxidant selected from cyclotrimethylenetrinitramine and cyclotetramethylene tetranitramine, or a mixture of two or more thereof.

In a certain embodiment, the oxidant added to the propellant composition of the present invention is cyclotrimethylenetrinitramine having an average particle size of about 3 to 6 μm.

In a certain embodiment, the oxidant contained in the propellant composition of the present invention may be added in an amount of 1 to 40 wt %, more specifically 5 to 35 wt %, and even more specifically 10 to 35 wt % to the total propellant composition.

The biggest problem of the propellant composition including the nitrocellulose binder and the nitramine oxidant is that it is difficult to form an extrudate because physical compatibility between the two materials is lacking, and when extruding the propellant shape after preparation, detrimental matters such as bubble generation in the extrudate, splitting of the extrudate surface, and clogging of perforation holes are observed. In order to effectively solve the problems, the present invention allows the addition of a plasticizer having both a nitrate group and a nitramine group to improve a physical compatibility between a nitrocellulose binder (having a nitrate group) and an oxidant (having a nitramine group), leading to remarkable improvement on the aforementioned disadvantages (See Examples).

In a certain embodiment, the plasticizer having both the nitramine group and the nitrate group includes alkyl nitrate ethyl nitramine (alkyl-NENA), dinitroxy diethyl nitramine (DINA), N,N′-2,5-dimethylethylene dinitramine (DMEDNA), N,N′-2,5-diethylethylene dinitramine (2,5-DNH) and N,N′-bis(2-nitratoethyl)ethylene dinitramine, more specifically alkyl-NENA and DINA, and most specifically, alkyl-NENA.

Initially, the NENA compound has been researched as a material which substitutes nitroglycerin. The compound as a hybrid molecule having a nitrate group and a nitramine group is less sensitive to impact and friction than nitroglycerin, and some material has a lower freezing point than nitroglycerin. In particular, NENA may be beneficially used in a propellant for guns and an insensitive munition rocket propellant composition since it has both nitrate and nitramine moieties. In addition, when NENA is used in the propellant composition, it is possible not only to provide a wide spectrum of combustion rate and ballistic performance in gun and rocket propulsion, but also to provide a lower freezing point than conventional nitrates, thereby capable of providing better mechanical characteristics at low temperature.

In a certain embodiment, the alkyl-NENA includes methyl-NENA, ethyl-NENA, propyl-NENA, butyl-NENA and pentyl NENA, but are not limited thereto. In the present invention, it is most preferable that the plasticizer having both the nitramine group and the nitrate group is butyl-NENA.

The butyl-NENA used as the plasticizer having both the nitramine group and the nitrate group in the present invention has lower energy than energy-containing other plasticizers typically used, for example including glycerol-2,4-dinitrophenylether dinitrate, trimethylolethylmethane trinitrate, nitroglycerin, 1,2,4-butanetriol trinitrate (BTTN), trimethanolethane trinitrate (TMETN), dipentaerythritol hexanitrate (DiPEHN), trimethylolpropane trinitrate (TMPTN) and diethylene glycol dinitrate (DEGDN), and is able to be decomposed at relatively low temperature.

In a certain embodiment, the plasticizer having both the nitramine group and the nitrate group contained in the propellant composition of the present invention may be added in an amount of 1 to 10 wt %, more specifically 1 to 5 wt % and even more specifically, 1 to 4 wt % to the total propellant composition.

In general, a nitrate group included in nitrocellulose, a plasticizer, and the like is naturally decomposed as time elapses, and accordingly, the resulting decomposition products further facilitate decomposition of the nitrate group to finally cause an ignition phenomenon. To prevent the ignition, a stabilizer contained in the propellant composition of the present invention may be utilized in any form of stabilizers ordinarily known in the art as a material which is first reacted with the decomposition product to inhibit decomposition of any further nitrate group.

In a certain embodiment, the stabilizer contained in the propellant composition of the present invention includes diphenylamine (DPA), 2-nitrophenylamine (2-NPA), 2-nitrodiphenylamine (2-NDPA), 4-nitrodiphenylamine (4-NDPA), para-N-methylnitroaniline (MNA), para-nitro-N-methylmethoxyaniline (pNMA), ethyl Centralite, methyl Centralite, Akadite I, Akadite II and carbamite, but are not limited thereto. More specifically, it is preferred that the stabilizer contained in the propellant composition of the present invention is ethyl Centralite or Akadiate II which is less toxic to the human body.

In a certain embodiment, the stabilizer contained in the propellant composition of the present invention may be in an amount of 0.1 to 5 wt %, more specifically 0.5 to 3 wt % in the total propellant composition, but is not limited thereto, and the content of the stabilizer may be appropriately adjusted depending on the use environment.

Meanwhile, the propellant composition of the present invention may also further include an additive in a small amount (for instance, less than 3 wt %), for example including an anti-inflammatory agent such as potassium sulfide and potassium nitrate, and so on.

The propellant composition of the present invention may be feasibly prepared according to a typically known method. Briefly, the propellant composition of the present invention was prepared by extruding the mixture after blending each constituent component, and the problems such as bubble generation and splitting of the extrudate surface were significantly improved by adding the plasticizer to the propellant composition for ameliorating the physical compatibility between a nitrocellulose binder and an oxidant, which were frequently developed when the propellant shape is prepared. Then, when the composition is applied to a 40-mm ammunition after final process, excellent interior ballistics characteristics were exhibited in a broad temperature range (for example, −40° C., 21° C., 52° C., and so forth) (See Table 1).

In a certain embodiment, the propellant composition of the present invention has stable interior ballistics characteristics in a range of low temperature to high temperature, more specifically in a temperature range of −40° C. to 52° C. in an ammunition for guns.

The features and advantages of this invention are summarized as follows:

(i) The present invention relates to a high energy-containing propellant composition and a use thereof.

(ii) The propellant composition of the present invention is a propellant composition for guns, including: (a) 55 to 85 wt % of a nitrocellulose binder; (b) 10 to 35 wt % of a nitramine oxidant; (c) 1 to 4 wt % of a plasticizer having both a nitrate group and a nitramine group; and (d) 0.5 to 3 wt % of a stabilizer.

(iii) The propellant composition of the present invention significantly improves a physical compatibility between the nitrocellulose binder and the oxidant using a plasticizer containing both a nitrate group and a nitramine group, leading to stable interior ballistics characteristics from low temperature to high temperature as well as improvement on the characteristics of an extrudate.

(iv) Accordingly, the propellant composition of the present invention may be effectively applied to an ammunition for guns due to an excellent material property and stability thereof.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a result showing a 7-hole cylindrical extrudate prepared using propellant compositions 1 and 2.

DETAILED DESCRIPTION OF THE INVENTION

Hereinafter, the present invention will now be described in further detail by examples. It would be obvious to those skilled in the art that these examples are intended to be more concretely illustrative and the scope of the present invention as set forth in the appended claims is not limited to or by Examples.

Example 1. Preparation of Propellant Compositions

As solvents, Acetone (Daejung Chemical & Metals Co., Ltd., Korea), ethyl acetate (Daejung Chemical & Metals Co., Ltd., Korea) and diethyl ether (Daejung Chemical & Metals Co., Ltd., Korea) were put into a Sigma Blade Mixer (Fine Machinery Ind. Co., Ltd., Korea), and then nitrocellulose (Hanwha Corporation, Korea) was added thereto and dissolved. After complete dissolution, a mixture containing a nitramine solid oxidant, a plasticizer and a stabilizer was added into the mixer and sufficiently mixed. The solvent was evaporated until the mixture had a suitable viscosity, and then the mixture was tightly sealed to prevent additional evaporation of the solvent. The kneaded/obtained mixture was put into a RAM PRESS (Boo Young Precision Tool Co., Ltd., Korea) equipped with a propellant mold, and was extruded by adding pressure thereto. After the extrudate was cut into a predetermined size to make a grain form, it was dried at normal temperature overnight, and then further dried at 50 to 60° C. for about 3 days. So as to prevent generation of static electricity in the propellant grains, graphite (Asbury Carbons, USA) was dry coated on the surface of the grain.

2. Constitution of Propellant Composition and Study on Characteristics Thereof

As described above, the constitutions of Composition 1, Composition 2, and a Control (Reference propellant) are as follows:

(a) Composition 1—Nitrocellulose 85%, RDX (Hanwha Corporation, Korea) 10%, BuNENA (Hanchem Co., Ltd., Korea) 3% and Akadite II (Synthesia, a.s, Czech Republic) 2%;

(b) Composition 2—Nitrocellulose 75%, RDX 20%, BuNENA 3% and Akadite II 2%; and

(c) Control (Reference propellant)—Single base propellant composed of nitrocellulose.

For the prepared propellants of Composition 1 and Composition 2, an abnormal phenomenon such as crumbling of the kneaded product did not occur during the mixture of raw materials, and the surface of the extrudate was smoothly extruded when the kneaded product was extruded as a 7-hole cylindrical form. Further, when a grain shape was produced by cutting the extrudate, an abnormal phenomenon such as bubble generation and clogging of perforation holes was not observed (See FIG. 1).

Subsequently, the present inventors investigated a change in interior ballistics characteristics according to the temperature by using the propellant grains of Composition 1 and Composition 2 to charge a 40-mm ammunition with the propellant.

TABLE 1 Comparison of Characteristics between Propellant Compositions of Present Invention and Conventional Single Base Propellant according to Change in Temperature. Classification −40° C. 21° C. 52° C. Composition Propellant charge 1 weight 390 g Muzzle velocity (m/s) 1250 1300 1330 Maximum pressure 300 334 351 in chamber (Mpa) Composition Propellant charge 2 weight 390 g Muzzle velocity (m/s) 1320 1360 1380 Maximum pressure 351 386 413 in chamber (Mpa) Reference Propellant charge Propellant weight 390 g (Single Base Muzzle velocity (m/s) 1250 1290 1320 Composition) Maximum pressure 305 344 364 in chamber (Mpa)

As can be confirmed in Table 1, the Propellant Compositions 1 and 2 exhibited stable interior ballistics characteristics at all the tested temperatures (−40° C., 21° C. and 52° C.) without any abnormal phenomenon such as an abnormal pressure increase in chamber. Further, when an ammunition was equally charged with the propellant charge weight of 390 g, the Propellant Composition 1 exhibited a suitable interior ballistics results as a propellant for use in guns, which had low maximum pressure and high muzzle velocity at all the tested temperatures compared with the Reference Propellant (Single Base Composition). In addition, it could be demonstrated that the Propellant Composition 2 is a high-energy propellant composition in which the muzzle velocity is remarkably enhanced at a normal temperature condition (21° C.) compared to the Reference Propellant. It is appreciated that the Propellant Compositions 1 and 2 may be efficiently used in a high-performance ammunition when considering the interior ballistics characteristics thereof.

Although the specific part of the present disclosure has been described in detail, it is obvious to those skilled in the art that such a specific description is just a preferred embodiment and the scope of the present invention is not limited thereby. Therefore, the substantial scope of the present disclosure will be defined by the appended claims and equivalents thereof. 

1. A propellant composition for guns, comprising: (a) 55 to 85 wt % of a nitrocellulose binder; (b) 10 to 35 wt % of a nitramine oxidant; (c) 1 to 4 wt % of a plasticizer having both a nitrate group and a nitramine group; and (d) 0.5 to 3 wt % of a stabilizer.
 2. The propellant composition of claim 1, wherein a nitrogen content in the nitrocellulose binder is 12 to 14 wt %.
 3. (canceled)
 4. (canceled)
 5. The propellant composition of claim 1, wherein the plasticizer having both the nitrate group and the nitramine group is alkyl-nitrate ethyl nitramine (alkyl-NENA).
 6. (canceled)
 7. The propellant composition of claim 1, wherein the propellant composition has stable interior ballistics characteristics at a temperature of −40° C. to 52° C. 